Pressure transducers fitted into the surface of the combustion chamber are used for researching and also monitoring combustion engines. Consequently their diaphragms are exposed not only to the gas pressure but also to severe thermal shocks resulting from the flame propagation, which overlay additional errors upon the actual pressure pattern. Thus the expansion phases are mostly measured with considerable errors.
For years designers of pressure transducers have therefore endeavoured to reduce the thermal shock effects to a minimum by means of thermally insulating covering layers, heat shields or multiple plate diaphragms. Such frontal protection usually involves placing additional mass before the sensor element, which may give rise to increased acceleration error signals so that valve impacts also produce a pressure error signal.
The thermal-shock-compensated diaphragm design according to the invention embodies a different approach by incorporating in the diaphragm parts that are as thin and therefore as light as possible. By means of the thermal component a light, elastic supporting structure in the form of a parallelogram which causes a distortion of the flexurally elastic central plate, the distortion mass of which is optimized so that the resulting double parallelograms impose a compensating action on the sensor transmission element, enabling the thermal shock to be largely compensated. Moreover the elastic design of the four main elements of the diaphragm structure:
the outer sleeve PA1 the annular plate PA1 the central plate PA1 and the annular support promotes optimal stress behavior for continuous operating states too in particular, by means of defined joint points. Instead of protecting the diaphragm parts against thermal effects by every means possible, the action of the thermal shocks is itself utilized to achieve a compensating effect by means of parallelogram displacement. The invention thus adopts an entirely new approach by deliberately exploiting the thermal distortion on a newly designed part of the diaphragm--the central plate --so that this distortion is diverted into a compensating movement by means of an intelligent supporting element.